1. Field of the Invention
This invention relates to a radiation image read-out apparatus provided with a film digitizer for photoelectrically reading out a radiation image, which has been recorded on a sheet of silver halide film, such as X-ray film, and thereby generating an image signal representing the radiation image.
2. Description of the Prior Art
Techniques for reading out a recorded image in order to obtain an image signal, carrying out appropriate image processing on the image signal, and then reproducing a visible image by use of the processed image signal have heretofore been known in various fields.
For example, as disclosed in Japanese Patent Publication No. 61(1986)-5193, a sheet of X-ray film having a small gamma value chosen according to the type of image processing to be carried out is used together with an intensifying screen, and an X-ray image is recorded on the X-ray film. The X-ray film, on which the X-ray image has been recorded, is subjected to a developing process. The X-ray image is then read out from the X-ray film and converted into an electric signal (image signal) by using a film digitizer (FD). The image signal is processed and then used for reproducing the X-ray image as a visible image on a copy photograph or the like. In this manner, a visible image having good image quality with high contrast, high sharpness, high graininess, or the like, can be reproduced.
When a radiation image is recorded on a sheet of silver halide film, such as X-ray film, and read out from the silver halide film by using a film digitizer, the silver halide film is exposed to radiation, and a latent image of the radiation image is thereby recorded on the silver halide film. Thereafter, the film, on which the radiation image has been recorded, is fed into a developing machine and subjected to a developing process, which is composed of a series of developing, fixing, washing, and drying steps. The radiation image is thereby developed into a visible image. The film, on which the visible radiation image has been recorded, is set at a predetermined position in the film digitizer, and the visible radiation image is read out from the film. For this purpose, the film, which has been fed out of the developing machine, must be manually set at the predetermined position in the film digitizer. Considerable time and labor are required to carry out such manual operations. Also, when the film is processed manually, the film will be stained with finger marks, dust, or the like. Therefore, when an image signal is detected from the film and used during the reproduction of a visible radiation image, the image quality of the visible radiation image thus reproduced cannot be kept high.